The application relates to liquid flow discharge nozzles, particularly of the type used in fire-fighting, where the reach of the discharge stream is of critical importance in properly controlling the fire. In fire-fighting techniques, it is frequently necessary to use a single hose line as soon as possible to initiate the extinguishing of the blaze pending the arrival or connection of additional hose lines as equipment becomes available. The addition of hose lines creates variations in the flow pressure in the hose lines which may lead to a common nozzle through some manifold arrangement. Also, there are variations in pumping pressure which not only affect a nozzle served by multiple hose lines, but also affect the reach of the stream discharged by a single hand line nozzle.
In order to avoid the fluctuations and variations in the reach of the nozzle discharge stream as a result of the above-mentioned factors, as well as other factors, it has been proposed that nozzles be provided with a pressure-responsive baffle which will either diminish or enlarge the discharge orifice of the nozzle in response to fluctuations in line pressure so as to maintain a fairly constant discharge pressure at the nozzle. Examples of such pressure-responsive nozzle structures, particularly intended for fire-fighting purposes, can be found in U.S. Pat. Nos. 3,539,112; 3,684,192; 3,863,844; 3,893,624 and 3,904,125.
Most of these prior art nozzles rely upon a yieldable or resilient means in the form of a spring or the like to oppose and control the fluid-pressure induced displacement of the baffle. As more fully disclosed hereinafter, this form of control results in a substantially linear rate of fluid-pressure control at the discharge orifice, within the broad range of volume of gallonage for which the nozzle is designed.
Others, disclosed in the prior art patents, introduce more complex and sophisticated structure in an effort to eliminate primary reliance upon mechanical spring retraction means and thereby overcome the control disadvantages which result from being compelled to follow a linear spring compression rate.